Photographic material having a roughened protective layer



3,443,946 PHOTOGRAPHIC MATERIAL HAVING A ROUGHENED PROTECTIVE LAYER Herbert Grabhiifer, Cologne-Flittard, and Giinter Meinhardt, Leverkusen, Germany, assignors to Agfa Aktiengesellschaft, Leverkusen, Germany, a corporation of Germany No Drawing. Filed May 13, 1965, Ser. No. 455,605 Claims priority, application Germany, June 4, 1964,

Int. Cl. G03c 1/72 US. Cl. 96--50 4 Claims ABSTRACT OF THE DISCLOSURE Protective layer for photographic material, which layer has a water-permeable binder containing particles of an acrylonitrile polymer plasticized with a beta-cyanoethyl ether of a polyhydric aliphatic alcohol or a phosphoric acid ester of pentaerythritol.

The invention relates to a photographic material having a transparent roughened protective layer.

It is known to provide photographic layers with protective coatings for protection against scratching and other harmful influences. Materials of very different chemical constitutions are used for these coatings. Generally, the light-sensitive emulsion side is coated with an outer thin gelatine layer. Other Water-soluble or alkali-soluble film formers, which are used in a known manner for this purpose, are for example other proteins, such as casein, partially hydrolyzed polyvinyl acetate, polyvinyl alcohol, polyvinyl phthalate, cellulose acetate phthalate and substances of high molecular weight which are of similar structure. All these substances have the disadvantage that, when they dry, they produce more or less smooth surfaces which are undesirable for many uses in the photographic art. For example, photographic materials provided with such protective coatings can only be retouched and written on with difficulty. Furthermore, Newtons rings are formed on printing or on projection. Smooth surfaces also have a tendency to become elec trostatically charged, causing local blackening on the light-sensitive layer. Many experiments have been carried out in an attempt to eliminate these disadvantage properties of smooth protective layers. Thus, it is known to incorporate starch in finely divided form into light-sensitive photographic layers. In addition, water-insoluble plastic particles of polystyrene, polyesters and similar synthetic materials of high molecular weight have been used for roughening the surface. It is true that all these measures lead to a detectable improvement in the writing capacity and reduce the formation of Newtons rings and electrostatic charges, but they also introduce other disadvantages, for example, a general clouding of the layers, which frequently shows in the form of spots, sedimentation of the plastic dispersion during casting and finally matting effects, which are particularly undesirable when producing transparent pictures.

It is an object of the invention to provide a protective layer which does not have the aforesaid disadvantages and which, with simple composition and processing, prevents the formation of Newtons rings and electrostatic charging and enables the photographic image to be written on or retouched.

It has now been found that a transparent protective layer with a roughened surface of the composition as indicated below, applied as an outer layer to the front and/or back of a light-sensitive photographic material, has properties which satisfy all requirements.

States atent The protective layer according to the invention contains the following components:

(I) Film-forming binding agent Suitable for this'purpose are numerous polymers which must be pervious to water and are capable of forming thin films. It is preferred to use gelatin, but this can be wholly or partially replaced by other products, such as casein, albumin, polyvinyl alcohol, partially hydrolyzed polyvinyl acetate, preferably having at the last 10 mol percent vinylacetate units, polyamides, polyvinyl pyrrolidone, carboxymethyl cellulose, alginic acid and derivatives thereof, such as salts, particularly alkali metal salts, esters preferably with lower aliphatic alcohols having up to 5 carbon atoms, or amides, carraghenates and similar substances.

(II) Polymer containing nitrile groups This component is heterogeneously distributed in the protective layer, but cannot be detected optically in the final layer by simply looking therethrough, or can only be detected by a very weak opalescence. The polymers contain acrylonitrile or methacrylonitrile units in polymerized form, advantageously in quantities of at least 50 mol percent.

Polyacrylonitrile or polymethacrylonitrile, more especially the former, are preferred. Suitable as components forcopolymers are for example acrylic acid esters or methacrylic acid esters with an aliphatic alcohol having up to about 6 carbon atoms, vinyl acetate, alkylvinyl ethers, of which the alkyl group contains up to 4 carbon atoms, and also N-vinylpyrrolidone, N-vinylimidazole, vinyl pyridine, acrylamide or methacrylamide. The grain size of the polymers to be used should be 1 to 25H, advantageously 1 to 5,u.

(III) Plasticizer The plasticizer prevents the optical detection of the particles of Component II. This effect is based on the fact that the smaller polymer particles, which would cause a clouding and matting, are completely solvated, but the larger particles are only softened on the surface.

This effect is restricted to plasticizers, which are characterized by a content of fi-cyanethoxy-and/or ethylene oxide groups. The following types of plasticizers exhibit particular utility:

(A) fl-Cyanoethyl ethers of polyhydric and advantageously dihydric to tetrahydric aliphatic alcohols advantageously containing up to 10 carbon atoms, for example, glycol, glycerine, pentaerythritol, diethylene glycol, triethylene glycol and the like. Suitable products are described in US. Patent 2,401,607. The following are mentioned as example:

(5) Di-fi-cyanoethyl ethers of pentaerythritol, of which the residual 2 hydroxyl groups have been reacted by acetalization with a ketone or aldehyde to form a 3 4 cyclic ether grouping of the m-dioxane type. These comous effect on the light-sensitive layers and can be used pounds have the general formula: with all types of black-and-white and color photographic (FOE, materials, phototechnical materials or photographic ele- C ments, which are to be used for making X-ray images.

The protective layers can be applied onto silver halide 043%: CHz-0-CHr-C r-CN emulsion layer, filter layers, anti-halo layers, non-curling wherein R and R represent hydrogen, alkyl advanlayers and the liketageously containing up to 6 carbon atoms, aryl, advan There is no dependence on the composition and the tageously phenyl, or heterocyclic radicals, such as number of the layers 0f the material Coatedpyrimidine or morpholine. These groups, more especial- 1O ly the phenyl rings or heterocyclic radicals, can contain EXAMPLE 1 further substituents, such as low alkyl or alkoxy having up to 3 carbon atoms or halogen atoms such as chlorine To 1 litre of 1% aqueous gelatine solution ready and the like. for casting, there are added 30 cc. of aqueous Suitable compounds and the preparation thereof are solution of plasticizer 1 and 1.5 cc. of a 10% aqueous described 1n British patent specification No. 926,689 and polyacrylonitrile suspension (prepared by the process dethe following is mentioned by way of example: scribed in German Patent 1,058,835) and intensively 0H; 0-CH CH -OCH CH -GN miXe-d. This casting solution is applied to that side of C O a photographic film which contains the light-sensitive 2O gelatine-silver halide emulsion layer and dried. A trans- 1 parent film is obtained, which layer can be satisfactorily (B) Phosphoric acid esters of pentaerythritol of the Written and Which has PTaetieaHY tendency to formula become electrostatically charged.

(fi/O-CE: /CHr-O\(") o-ohi CHz-O in which formula, R and R which may be the same or different, represent alkyl, cyanoalkyl and especially EXAMPLE 2 cyanoethyl, with up to 18 carbon atoms, or aryl such as Of a 10% q eolullon 0f Plastleller 3 phenyl, and n=1-20, advantageously 1 10. These comd 3 of an aqueous Suspenswn f pq y l pounds and the preparation thereof are described in conslstmg of 60 H101 Percent of acrylomtrlle umts and British patent specification No, 922,251, a d Belgian 40 mol percent of methyl methacrylate emulsion (prepatent specification No. 636,304. The following are men- 35 pared y the Pfoeess of German Patent 1,053,335)

tioned as examples: are mixed and added to 1 litre of a 1% aqueous gelatine (6) (6 0 0%? NC-CHPCH20CH2CH20-P x PO--CHr-CH:OC 2CH2 The protective layers consisting of the above three solution which is ready for casting. This solution is cast components advantageously should contain (per 100 onto the silver halide emulsion layer and the rear of parts of the film-forming component I such as gelatine), a photographic material. The dried layers are free from 5-200 parts of plasticizer and 0.5 to 10 parts of polymer. Newtons rings when in contact with glass. More especially suitable are those mixtures which contain 10-50 parts of plasticizers and 1-3 parts of polymer [EXAMPLE 3 II, per 100 parts of gelatlne.

In carrying out the process according to the invention,

the aqueous dispersions of the polymers are incorporated 35 of a 10% aqueous Solution of Plastieiler 7 and by stirring, together with the plasticizers, into the binder a 10% aqueous Solution 9 Plasticizfir f solution which can be provided with the usual casting mlxed 2 of aqPeous 10% polyacrYlomtnle additives. Using this casting solution, the photographic P P Q addefi to 1 mm of a gelatme P film material is coated on the light-sensitive silver halide tlon- Thls mlxtura 15 cast on both sldes to the 811V emulsion layer and/or on the rear side by known casting 6D ha1 ide emulsion layers of P P P eY ThlS film can be satisfactorily wrltten on and is charmethods. t

The mixing ratio between polymer Proportion and acterized by an excellent antistatic action, by complasticizer proportion depends on the required degree of Panson with a film mammal havmg a P gelatme P tective layer.

roughness and can be 1:1 to 1:100, advantageously 1:5 After air condifioning Specimens of the film at 35 to 1:20. The mixture of these substances is added in such a concentration to the outer protective layer that 0.1 to 5 m air hmPidity and electrostatic ts" Square metre are contained i the dried layen mg in v./cm. is measured with a rotating field strength The protective layers should have a thickness of about measuring instrument according sehwen'khagen and 0.5 to 15 the electric surface resistivity in ohms is measured with The protective layers of the invention have no deleteria knife-edge instrument.

RES ULT Charging Surface capacity resistivity (v./cm.) (10 52) Control specimen +420 13 Specimen according to Example 3 1. 5

where R and R are alkyl, cyanoalkyl or phenyl and each n is a number from 1 to 20.

2. The combination of claim 1 in which the plasticizer is a beta-cyanoethyl ether of a polyhydric alcohol having up to ten carbon atoms and two to four alcohol groups.

3. The combination of claim 1 in which the plasticizer is R2 OCH2 CH2OCH2CN in which R and R are hydrogen, alkyl containing up to six carbon atoms, or aryl.

4. The combination of claim 1 in which the plasticizer is (b) where R and 'R are alkyl with up to 18 carbons or cyanoethyl and each n is a number from 1 to 10.

References Cited UNITED STATES PATENTS 2,401,607 6/1946 Bruson 260465.6 3,079,257 2/1963 Morcher et a1 9648 3,158,643 11/1964 Fulmer et al 26032.4 3,219,616 11/1965 Saxon 26032.4 3,364,044 1/1968 Grabhofer et a1 96-114 3,364,285 1/1968 Grabhofer et a1 96-1 14 FOREIGN PATENTS 922,251 3/ 1963 Great Britain.

926,689 5/1963 Great Britain.

933,391 8/1963 Great Britain.

752,791 7/ 1956 Great Britain.

J. TRAVIS BROWN, Primary Examiner.

CAROLYN E. DAVIS, Assistant Examiner.

US. 01. X.R. 96-48, 67, 87, 114 

